Silver halide reproduction materials which contain disulfide compounds substituted by two heterocyclic radicals are known and are described, e.g., in U.S. Pat. Nos. 2,440,110 and 2,465,149. These serve to prevent fogging of silver halide emulsions and/or to improve the fog-lowering effect of sulfinic or seleninic acids.
Silver halide materials which contain thiazolidine carboxylic acids are likewise known and described, e.g., in U.S. Pat. No. 3,565,625. They are used here to improve the sensitivity-fogging ratio. Moreover, it is stated in P. Glafkides, Chimie et Physique Photographiques, 3d edition, Paris, 1967, p. 313, that thiazolidine carboxylic acids act as contrast-modifying desensitizers whereby negative emulsions are desensitized, while with positive emulsions gradation is elevated at the cost of sensitivity.
It is, moreover, known that in the development of a light-sensitive silver halide reproduction material the silver formed, and thus also gradation, which largely determines the image character, depends to a great extent on development conditions, especially on time and temperature of development. Therefore, it is endeavored to keep the time and temperature of development as constant as possible. In actual practice, however, this has not been possible to a satisfactory degree.
Gradation stability is of special significance in the development of x-ray films where for diagnostic reasons a high constancy of gradation is required. Today, as a result of the short development times used, these are very susceptible to deviations of development conditions, especially against overdevelopment. Thus, the task of the present invention is to provide a light-sensitive silver halide reproduction material which excels in high gradation stability during development under various conditions.